Honeycomb structure

Abstract

The utility model provides a honeycomb structural body which is used as a filter for purifying waste gas and can restrain the rise of pressure loss when PM (particulate matter) of coal and the like is accumulated. A honeycomb structure is provided with a columnar honeycomb structure part (4) having partition walls (1) arranged so as to surround a plurality of cells (2) that serve as fluid flow paths and extend from a first end surface (11) to a second end surface (12), and the partition walls (1) are configured from a porous body in which a plurality of pores that communicate adjacent cells (2) with each other with the partition walls (1) therebetween are formed. The ratio L / T of the flow path length L of the pores in the thickness direction of the partition walls (1) to the thickness T of the partition walls (1) is defined as the curvature A, the unit of L and T is [mu] m, the average curvature AAve, which is the average value of the curvature A of the partition walls (1) constituting the honeycomb structure part (4), is 1.10-1.40, and the value X (X = AAve / B2) obtained by dividing the average curvature AAve by the square of the deviation curvature B, which is the deviation of the curvature A, is 100-300.

Description

Technical Field

[0001] The present utility model relates to a honeycomb structure. More specifically, it relates to a honeycomb structure that can suppress an increase in pressure loss during PM accumulation such as coal when used as a filter for exhaust gas purification. Background Art

[0002] Conventionally, as a filter for capturing particulate matter in exhaust gas discharged from internal combustion engines such as automobile engines and a device for purifying toxic gas components such as CO, HC, and NOx, a honeycomb filter using a honeycomb structure has been known. The honeycomb structure has partition walls made of a porous ceramic such as cordierite, and a plurality of compartments are formed by partitioning through the partition walls. The honeycomb filter is arranged with a sealing portion in such a way that the openings on the inflow end face side and the openings on the outflow end face side of the plurality of compartments are alternately sealed. That is, the honeycomb filter has a structure in which an inflow compartment with an open inflow end face side and a sealed outflow end face side and an outflow compartment with a sealed inflow end face side and an open outflow end face side are alternately arranged with the partition wall in between. And in the honeycomb filter, the porous partition wall functions as a filter for capturing particulate matter in the exhaust gas. Hereinafter, the particulate matter contained in the exhaust gas is sometimes referred to as "PM". "PM" is an abbreviation for "particulate matter".

[0003] Regarding the honeycomb filter using a honeycomb structure, due to the strengthening of exhaust gas regulations and the like, various studies have been conducted to improve the capture performance of capturing PM while requiring a low pressure loss (for example, refer to Patent Document 1).

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2020-54985 Summary of the Utility Model

[0007] Problems to be Solved by the Utility Model

[0008] For example, as a method for reducing the pressure loss of a honeycomb filter, a method of increasing the porosity of the porous partition wall constituting the honeycomb structure can be cited. However, if only the porosity of the partition wall is increased, the capture performance as a filter decreases. Thus, conventionally, it has been considered that increasing the porosity of the honeycomb filter to reduce the pressure loss and improving the capture performance of capturing PM are in a contradictory relationship, and it is very difficult to solve both at the same time. Therefore, there is an urgent need to develop a honeycomb structure for a honeycomb filter that can effectively suppress an increase in pressure loss during PM accumulation such as coal while maintaining the porosity of the partition wall.

[0009] The present utility model has been completed in view of the problems of such prior art. According to the present utility model, there is provided a honeycomb structure which can suppress an increase in pressure loss when PM such as coal accumulates, in the case of being used as a filter for exhaust gas purification.

[0010] Solution for Solving the Problem

[0011] According to the present utility model, there is provided the honeycomb structure shown below.

[0012] [1] A honeycomb structure, characterized in that

[0013] it includes a columnar honeycomb structure portion having partition walls arranged in a manner to surround a plurality of compartments serving as fluid flow paths extending from a first end face to a second end face,

[0014] the partition walls are made of a porous body, and the porous body is formed with a plurality of fine pores that communicate the adjacent compartments sandwiching the partition walls with each other,

[0015] a ratio L / T of a flow path length L of the fine pores in a thickness direction of the partition wall to a thickness T of the partition wall is defined as a tortuosity A, where the units of the flow path length L and the thickness T are μm,

[0016] an average value of the tortuosity A of the partition walls constituting the honeycomb structure portion, that is, an average tortuosity A Ave is 1.10 to 1.40, and

[0017] the average tortuosity A Ave divided by a square of a deviation of the tortuosity A, that is, a deviation tortuosity B, a value X obtained is 100 to 300, where X = A Ave / B 2 .

[0018] [2] The honeycomb structure according to the above [1], characterized in that

[0019] it further includes a plugging portion disposed at an opening portion on a first end face side or a second end face side of each of the compartments.

[0020] [3] The honeycomb structure according to the above [1] or [2], characterized in that

[0021] a thickness T1 of the partition wall is 100 to 300 μm.

[0022] [4] The honeycomb structure according to the above [1] or [2], characterized in that

[0023] a porosity of the partition wall is 35 to 70%.

[0024] [5] The honeycomb structure according to [1] or [2] above is characterized in that

[0025] The average pore diameter of the partition wall is 8 to 30 μm.

[0026] [6] The honeycomb structure according to [1] or [2] above is characterized in that

[0027] X is 150 to 300.

[0028] Effect of the utility model

[0029] The honeycomb structure of the present utility model has the effect of suppressing the increase in pressure loss during the accumulation of PM such as coal when used as a filter for waste gas purification. In particular, the honeycomb structure of the present utility model has the remarkable effect of suppressing the increase in pressure loss during PM accumulation without the need to maintain the porosity of the partition wall, that is, by improving the porosity of the partition wall in a special way. Description of the drawings

[0030] Figure 1 is a perspective view schematically showing an embodiment of the honeycomb structure of the present utility model.

[0031] Figure 2 is from Figure 1 The top view observed from the first end face side of the honeycomb structure shown.

[0032] Figure 3 is schematically showing Figure 2 The cross-sectional view of the A-A' section of.

[0033] Figure 4 is an enlarged cross-section of the partition wall and is a schematic diagram for explaining the flow path length of the pores formed in the porous body constituting the partition wall. Detailed implementation manners

[0034] Hereinafter, embodiments of the present utility model will be described, but the present utility model is not limited to the following embodiments. Therefore, it should be understood that, within the scope not departing from the gist of the present utility model, the following embodiments are appropriately modified and improved based on the general knowledge of those skilled in the art, and such modified and improved embodiments also fall within the scope of the present utility model.

[0035] (1) Honeycomb structure:

[0036] An embodiment of the honeycomb structure of the present utility model is as Figures 1 to 3The honeycomb structure 100 having a columnar honeycomb structure portion 4 is shown. The columnar honeycomb structure portion 4 has a porous partition wall 1. The honeycomb structure portion 4 is a columnar honeycomb structure, which has a porous partition wall 1 arranged in a manner of surrounding a plurality of compartments 2 that form fluid flow paths extending from the first end face 11 to the second end face 12. In the honeycomb structure 100, the honeycomb structure portion 4 is columnar and also has an outer peripheral wall 3 on its outer peripheral side surface. That is, the outer peripheral wall 3 is arranged in a manner of surrounding the partition wall 1 arranged in a lattice pattern.

[0037] Among them, Figure 1 is a perspective view schematically showing an embodiment of the honeycomb structure of the present utility model. Figure 2 is from Figure 1 the top view observed from the first end face 11 side of the shown honeycomb structure 100. Figure 3 is schematically showing Figure 2 the cross-sectional view of the A-A' section of

[0038] Figures 1 to 3 The shown honeycomb structure 100 further includes a plugging portion 5 arranged at the opening portion on the first end face 11 side or the second end face 12 side of each compartment 2, and can be used as a filter for waste gas purification.

[0039] The plugging portion 5 is arranged at the opening portion on the first end face 11 side or the second end face 12 side of each compartment 2. Figures 1 to 3 In the shown honeycomb structure 100, the plugging portion 5 is arranged at the opening portion on the first end face 11 side of a predetermined compartment 2 and the opening portion on the second end face 12 side of the remaining compartments 2. Among them, when the first end face 11 is set as the inflow end face and the second end face 12 is set as the outflow end face, the compartment 2 with the plugging portion 5 arranged at the opening portion on the outflow end face side and opening on the inflow end face side is set as the inflow compartment 2a. In addition, the compartment 2 with the plugging portion 5 arranged at the opening portion on the inflow end face side and opening on the outflow end face side is set as the outflow compartment 2b. The inflow compartment 2a and the outflow compartment 2b are preferably arranged alternately with the partition wall 1 in between. Moreover, thereby, it is preferably to form a grid pattern at both end faces of the honeycomb structure 100 by the plugging portion 5 and the "opening portion of the compartment 2".

[0040] Regarding the structure of the partition wall 1 constituting the honeycomb structure portion 4, the honeycomb structure 100 has a particularly important structure. First, in the honeycomb structure 100, the partition wall 1 constituting the honeycomb structure portion 4 is as Figure 4 shown, composed of a porous body formed with a plurality of fine holes 16 that communicate the adjacent compartments 2 sandwiching the partition wall 1 with each other. Among them, Figure 4 is the enlarged cross-section of the partition wall 1 and is a schematic diagram for explaining the flow path length L of the fine holes 16 formed on the porous body constituting the partition wall 1.

[0041] Among them, asFigure 4 As shown, two adjacent compartments 2 are partitioned by a partition wall 1 made of a porous body. The thickness of the partition wall 1 that partitions the two adjacent compartments 2 in this way is defined as "the thickness T (μm) of the partition wall 1". In addition, the flow path length of the pores 16 in the thickness direction of the partition wall 1 is defined as "the flow path length L (μm) of the pores 16". Moreover, the ratio (L / T) of the flow path length L (μm) of the pores 16 in the thickness direction of the partition wall 1 to the thickness T (μm) of the partition wall 1 is defined as "the tortuosity A". Hereinafter, the tortuosity A may sometimes be referred to as "the tortuosity A of the pores 16".

[0042] The tortuosity A of the pores 16 formed in the partition wall 1 is an index indicating the degree of bending of the pores 16 formed in the porous body constituting the partition wall 1. The pores 16 formed in the porous body constituting the partition wall 1 are the flow paths for the exhaust gas to pass through the partition wall 1, and the degree of bending of the flow paths can be shown by the "tortuosity A".

[0043] The average value of the tortuosity A of the partition wall 1 constituting the honeycomb structure portion 4, that is, the average tortuosity A Ave is 1.10 to 1.40. In addition, the average tortuosity A Ave divided by the square of the deviation of the tortuosity A, that is, the deviation tortuosity B, to obtain a value X (X = A Ave / B 2 ) is 100 to 300. By configuring in this way, when the honeycomb structure 100 is used as a filter for exhaust gas purification, it is possible to effectively suppress the increase in pressure loss during PM accumulation such as coal. In particular, without the need for a special method such as increasing the porosity of the partition wall 1, it is possible to extremely effectively suppress the increase in pressure loss during PM accumulation. That is, by setting the average tortuosity A Ave within the above numerical range, the average tortuosity A Ave shows a relatively small value, and the airflow through the pores 16 in the partition wall 1 becomes straighter, and it is possible to suppress the increase in pressure loss during PM accumulation while maintaining the porosity of the partition wall 1. In addition, by setting the value X obtained by dividing the above average tortuosity A Ave by the square of the deviation tortuosity B within the above numerical range, the deviation of the tortuosity A becomes smaller, that is, the deviation of the tortuosity A becomes smaller, and the proportion of the specific pores 16 in which the tortuosity A becomes extremely large in the pores 16 in the partition wall 1 becomes smaller, and it is easier to exhibit the effect of suppressing the increase in pressure loss.

[0044] The average tortuosity A Ave only needs to be 1.10 to 1.40, preferably 1.10 to 1.35, and more preferably 1.10 to 1.30. For example, if the average tortuosity A AveIf it is less than 1.10, the air flow becomes too straight, which may have an adverse effect on the PM capture performance and is not preferred in this regard. On the other hand, if the average curvature A Ave exceeds 1.40, it is difficult to obtain the effect of suppressing the increase in pressure loss during PM accumulation.

[0045] In addition, the value X obtained by dividing the average curvature A Ave by the square of the deviation curvature B (X = A Ave / B 2 ) should be 100 to 300, preferably 150 to 300, and more preferably 200 to 300. For example, when the value X is outside the above numerical range, it is difficult to obtain the effect of suppressing the increase in pressure loss during PM accumulation. It is preferred that when the above value X is 150 to 300, the deviation of the pressure loss increase rate caused by PM accumulation is suppressed to be small.

[0046] The curvature A of the pore 16 and the average curvature A which is the average value of the curvature A Ave can be measured by the following method.

[0047] Specifically, first, a CT scan is performed on the partition 1 of the honeycomb structure 100 to obtain a scanned image of the partition 1. As the CT scanning device, Xradia520Versa (trade name) manufactured by ZEISS is used. The measurement conditions are a tube voltage of 60 kV and a tube current of 0.083 mA. The resolution of the captured image is 1.2 μm / pixel.

[0048] The scanning direction in the CT scan is the direction along the thickness direction of the partition 1, and from the surface of the partition 1 on the side of the compartment 2 (for example, the inflow compartment 2a) that opens at the first end face 11 which is the upstream end face of the honeycomb structure portion 4 (hereinafter, appropriately referred to as the partition surface) toward the surface of the partition 1 on the side of the compartment 2 (for example, the outflow compartment 2b) that opens at the second end face 12 which is the downstream end face (hereinafter, appropriately referred to as the partition back face). Hereinafter, the scanning direction in the CT scan may sometimes be referred to as the "scanning direction S".

[0049] In the following description, the direction in which the compartment 2 of the honeycomb structure portion 4 extends (in other words, the direction from the first end face 11 to the second end face 12 of the honeycomb structure portion 4) is set as the Y direction. Moreover, the direction perpendicular to the Y direction and along the direction surrounding one of the four partitions 1 that surround the outflow compartment 2b is set as the X direction. The direction perpendicular to the X direction and the Y direction is set as the Z direction. Therefore, the above scanning direction S can be referred to as the Z direction. For example, the scanned image in the Z direction is along the X-Y plane.

[0050] Next, the group of captured images in the scanning direction S is used for analysis. The group of captured images in the scanning direction S refers to the group of the number of captured images in the scanning direction S, which is the thickness (μm) of the partition wall 1 divided by 1.2 μm of the size of 1 pixel. In the following example, the range of the X and Y planes of the analyzed image size is 500 μm × 500 μm. Regarding the Z direction, the number of images equivalent to the value obtained by dividing the thickness (μm) of the partition wall 1 by 1.2 μm is used.

[0051] Next, the captured images in the scanning direction S are binarized. Binarization is an operation for distinguishing the void part with the micropores 16 formed in the partition wall 1 from the solid part of the partition wall 1. Since the brightness of the void part and the solid part of the partition wall 1 is different from each other, in the binarization process, the noise remaining in the captured images is removed, and after setting an arbitrary threshold value, the binarization process is performed. The threshold value varies depending on each measurement sample. Therefore, by the mode method, a threshold value capable of separating the void part and the solid part is set for each captured image. In addition, the mode method refers to a method of finding the concentration boundary on the premise that the binary image is composed of two "objects" and "backgrounds" observed.

[0052] As described above, a three-dimensional model of the porous body constituting the partition wall 1 is obtained. That is, through the above binarization process, the spatial voxels or object voxels are obtained for each coordinate, and thus three-dimensional porous body data (i.e., a three-dimensional model of the porous body) can be obtained.

[0053] Next, fluid analysis is performed on the obtained three-dimensional model of the porous body constituting the partition wall 1 using the lattice Boltzmann method. Using the obtained flow velocity results, based on the flow velocity (u n , y n , z n ) [m, m, m] at the position, the position (x n , v n , W n ) [m / s, m / s, m / s], the position (x n+1 , y n+1 , z n+1 ) [m, m, m] after Δt seconds [s] is calculated by the following formula, and thus the flow path length of each streamline is calculated. In addition, a calculation example with the unit of position set to [m] is shown here, but the unit of position can also be set to [μm] as appropriate.

[0054] [Equation 1]

[0055] x (1) = x n

[0056] x (2) = x n +Δta 21 u(1)

[0057] x (3) = x n + Δt { a 31 u (1) + a 32 u (2)}

[0058] x (4) = x n + Δt { a 41 u (1) + a 42 u (2) + a 43 u (3)}

[0059] x n+1 = x n + Δt { b1u (1) + b2u (2) + b3u (3) + b4u (4)}

[0060] The value obtained by dividing the flow path length of each calculated streamline by the thickness of partition wall 1 is the degree of curvature A of each streamline, and the average value of each degree of curvature A is set as the average degree of curvature A Ave .

[0061] In addition, the deviation of the degree of curvature A, i.e., the deviation degree of curvature B, can be calculated by taking the root mean square (√) of each deviation.

[0062] The thickness T of partition wall 1 is not particularly limited. For example, it is preferably 100 to 300 μm, more preferably 125 to 275 μm, and particularly preferably 150 to 250 μm. The thickness of partition wall 1 can be measured using, for example, a scanning electron microscope or a microscope. When the thickness of partition wall 1 is too thin, the trapping performance deteriorates, which is not preferable. On the other hand, when the thickness of partition wall 1 is too thick, the pressure loss increases, which is not preferable.

[0063] The porosity of partition wall 1 is not particularly limited. For example, it is preferably 35 to 70%, more preferably 35 to 65%, and particularly preferably 35 to 60%. By configuring in this way, the honeycomb structure 100 can be suitably used as a filter for purifying the exhaust gas discharged from an automobile engine. The porosity of partition wall 1 is a value measured by the mercury intrusion method. The porosity of partition wall 1 can be measured using, for example, Autopore 9500 (trade name) manufactured by Micromeritics. The measurement of the porosity can be performed using a specimen piece obtained by cutting out a part of partition wall 1 from the honeycomb structure portion 4.

[0064] There is no particular limitation on the average pore diameter of the partition wall 1 adjacent thereto, and it is preferably 8 to 30 μm, more preferably 8 to 25 μm. The average pore diameter of the partition wall 1 is a value measured by the mercury intrusion method. The measurement of the average pore diameter of the partition wall 1 can be carried out, for example, using Autopore 9500 (trade name) manufactured by Micromeritics, by the same method as the measurement of the porosity.

[0065] The cell density of the cell 2 partitioned and formed by the partition wall 1 is, for example, preferably 30 to 65 cells / cm 2 , more preferably 40 to 55 cells / cm 2 . By configuring in this way, the honeycomb structure 100 can be suitably used as a filter for purifying the exhaust gas discharged from the engine of an automobile.

[0066] There is no particular limitation on the shape of the cell 2 formed in the honeycomb structure portion 4. For example, as the shape of the cell 2 in the cross section of the cell 2 orthogonal to the extending direction, polygons, circles, ellipses, etc. can be cited. As polygons, triangles, quadrilaterals, pentagons, hexagons, octagons, etc. can be cited. In addition, the shape of the cell 2 is preferably a triangle, a quadrilateral, a pentagon, a hexagon, or an octagon. In addition, in the present utility model, the cell 2 refers to the space surrounded by the partition wall 1.

[0067] Regarding the shape of the cell 2 formed on the honeycomb structure portion 4, the shapes of all the cells 2 can be the same or different. For example, although not shown, there may also be a cell in which a quadrilateral cell and an octagonal cell coexist. For example, it can be configured such that in the cross section of the honeycomb structure portion orthogonal to the extending direction of the cell, the shape of the outflow cell is different from the shape of the inflow cell. In such a manner, for example, it is preferable that the shape of the outflow cell is either a quadrilateral or an octagon, and the shape of the inflow cell is the other of a quadrilateral or an octagon.

[0068] In addition, regarding the size of the cell 2 formed on the honeycomb structure portion 4, the sizes of all the cells 2 can be the same or different. For example, although not shown, the size of a part of the cells among a plurality of cells can be increased, and the size of the other cells can be relatively decreased.

[0069] The outer peripheral wall 3 of the honeycomb structure portion 4 can be integrally formed with the partition wall 1, or can be an outer peripheral coating formed by coating an outer peripheral coating material on the outer peripheral side of the partition wall 1. For example, although not shown, the outer peripheral coating can be formed by integrally forming the partition wall and the outer peripheral wall during manufacturing, and then removing the formed outer peripheral wall by a known method such as grinding, and then disposed on the outer peripheral side of the partition wall.

[0070] There is no particular limitation on the shape of the honeycomb structural part 4. As the shape of the honeycomb structural part 4, columnar shapes such as a circular shape, an elliptical shape, and a polygonal shape can be cited for the first end face 11 (for example, the inflow end face) and the second end face 12 (for example, the outflow end face).

[0071] There is no particular limitation on the size of the honeycomb structural part 4, such as the length from the first end face 11 to the second end face 12 and the size of the cross section of the honeycomb structural part 4 orthogonal to the direction in which the compartments 2 extend. When the honeycomb structure 100 is used as a filter for exhaust gas purification, each size can be appropriately selected in such a way as to obtain the best purification performance.

[0072] There is no particular limitation on the material of the partition wall 1, as long as the average curvature A Ave , and the average curvature A Ave The value X obtained by dividing by the square of the deviation curvature B satisfies the above numerical range. For example, as the material of the partition wall 1, it is preferably a material containing at least one selected from the group consisting of silicon carbide, cordierite, silicon-carbide composite material, cordierite-carbide composite material, silicon nitride, mullite, alumina, and aluminum titanate. The material constituting the partition wall 1 is preferably a material containing 90% by mass or more of the materials listed in the above group, more preferably a material containing 92% by mass or more, and particularly preferably a material containing 95% by mass or more. In addition, the cordierite-carbide composite material is a composite material formed with silicon carbide as the aggregate and cordierite as the binder. In addition, the cordierite-carbide composite material is a composite material formed with silicon carbide as the aggregate and cordierite as the binder. As the material of the partition wall 1, particularly cordierite and silicon-carbide composite materials among the above materials can be cited as preferred materials.

[0073] The material of the plugging part 5 is preferably the material preferred as the material of the partition wall 1. The material of the plugging part 5 and the material of the partition wall 1 may be the same material or different materials.

[0074] (2) Manufacturing method of the honeycomb structure:

[0075] Next, the manufacturing method of the honeycomb structure of the present embodiment will be described. For example, the honeycomb structure of the present embodiment can be manufactured by the following manufacturing method. First, a plastic clay for preparing the honeycomb structural part is prepared. The clay for preparing the honeycomb structural part can be prepared, for example, as follows.

[0076] It can be prepared by appropriately adding additives such as binders, pore-forming materials, and water to the materials selected from the preferred material group of the aforementioned partition walls as raw material powders. In addition, by adjusting the particle size of silicon carbide that becomes the aggregate in the raw material powder used, the "bending degree A" of the partition walls in the honeycomb structure of the present embodiment described above can be changed. For example, although not particularly limited, there is a tendency that the finer the particle size of silicon carbide that becomes the aggregate, the more uniform the microstructure, and the smaller the bending degree A.

[0077] Next, by extruding and forming the clay thus obtained, a honeycomb formed body is prepared which has partition walls that partition and form a plurality of compartments, and an outer wall that is disposed so as to surround the partition walls.

[0078] The obtained honeycomb formed body is dried using, for example, microwaves and hot air. Next, if necessary, the openings of the compartments are sealed with the same material as that used for preparing the honeycomb formed body, thereby preparing a sealing portion. After preparing the sealing portion, the honeycomb formed body can be further dried.

[0079] Next, the honeycomb formed body or the honeycomb formed body provided with the sealing portion is calcined, thereby manufacturing a honeycomb structure. The calcination temperature and the calcination atmosphere vary depending on the raw materials, and those skilled in the art can select the calcination temperature and the calcination atmosphere that are most suitable for the selected materials.

[0080] Through the manufacturing method as described above, the honeycomb structure of the present embodiment can be manufactured.

[0081] [Examples]

[0082] Hereinafter, the present utility model will be described more specifically by way of examples, but the present utility model is not limited by any of these examples.

[0083] (Example 1)

[0084] As the forming raw materials for preparing the clay, talc, kaolin, alumina, aluminum hydroxide, silica, etc. are prepared. In Example 1, a cordierite-forming raw material was prepared by mixing the above-mentioned respective raw materials.

[0085] Next, 2.0 parts by mass of a water-absorbing polymer, 6 parts by mass of a binder, 1.0 part by mass of a surfactant, and 70 parts by mass of water are added as pore-forming materials to 100 parts by mass of the forming raw materials, and the clay is prepared. As the water-absorbing polymer used as the pore-forming material, a water-absorbing polymer having a particle size of 10 μm is used. Methylcellulose is used as the binder. Potassium laurate soap is used as the dispersant.

[0086] Next, the obtained green clay was formed using an extrusion molding machine to prepare a honeycomb formed body. Next, after high-frequency induction heating and drying the obtained honeycomb formed body, it was further dried using a hot air dryer. The shape of the compartments in the honeycomb formed body was quadrilateral.

[0087] Next, a sealing portion was formed in the dried honeycomb formed body. First, a mask was applied to the inflow end face of the honeycomb formed body. Next, the end portion (the end portion on the inflow end face side) to which the mask was applied was immersed in the sealing slurry, and the sealing slurry was filled in the openings of the compartments (outflow compartments) where the mask was not applied. Thus, a sealing portion was formed on the inflow end face side of the honeycomb formed body. Then, a sealing portion was similarly formed in the inflow compartments on the outflow end face of the dried honeycomb formed body as well.

[0088] Next, the honeycomb formed body having the sealing portion formed thereon was dried using a microwave dryer, and after further drying it completely using a hot air dryer, both end faces of the honeycomb formed body were cut to adjust to a predetermined size. Next, the dried honeycomb formed body was degreased and calcined to fabricate the honeycomb structure of Example 1.

[0089] The diameter of the end face of the honeycomb structure of Example 1 was 266.7 mm, and the length in the extending direction of the compartments was 254.0 mm. In addition, the thickness T of the partition walls was 156 μm, and the compartment density was 47 pieces / cm 2 . The value of the thickness T of the partition walls is shown in Table 1.

[0090] For the honeycomb structure of Example 1, the porosity and average pore diameter of the partition walls were measured. The respective results are shown in Table 1. In addition, the porosity and average pore diameter of the partition walls were measured using Autopore 9500 (trade name) manufactured by Micromeritics.

[0091] In addition, regarding the honeycomb structure of Example 1, the average tortuosity A Ave and the deviation tortuosity B were obtained by the method described above. Then, the value X (X = A Ave / B Ave ^2) obtained by dividing the average tortuosity A by the square of the deviation tortuosity B was calculated. The respective values are shown in Table 1. 2 )

[0092] [Table 1]

[0093]

[0094] Regarding the honeycomb structure of Example 1, the "initial pressure loss value P0 (Pa)", the "pressure loss value P1 (Pa) after PM deposition", the "pressure loss increase amount ΔP (Pa)" and the "pressure loss increase rate (%)" caused by PM deposition were obtained by the following method. The results are shown in Table 1.

[0095] 〔Initial pressure loss value P0 (Pa)〕

[0096] The center points of the voxels of the porous body three-dimensional data were set as the respective grid points, and fluid analysis based on the lattice Boltzmann method was performed. This lattice Boltzmann method used a predetermined relational expression related to the flow of fluid between each grid point and its adjacent grid point when the fluid flowed in from the inflow end face. The pressure difference between the inflow end face and the outflow end face was calculated as the initial pressure loss value P0 (Pa).

[0097] 〔Pressure loss value P1 (Pa) after PM accumulation〕

[0098] Based on the results of the fluid analysis, a velocity vector composed of the flow velocity and the flow direction was derived for each spatial voxel of the porous body three-dimensional data as information related to the flow of fluid in each spatial voxel. Next, the state in which PM (soot) was carried in the fluid flow shown by this velocity vector was simulated to predict the movement of PM. At this time, PM approaching the object voxel was captured by this object voxel. When PM accumulated about 1% of the pore volume, fluid analysis was performed again to obtain the pressure loss value P1 (Pa) after PM accumulation.

[0099] 〔Increase amount ΔP (Pa) of pressure loss after PM accumulation〕

[0100] The difference between the initial pressure loss value P0 (Pa) and the pressure loss value P1 (Pa) after PM accumulation obtained by the above method (i.e., P1 - P0) was set as the increase amount ΔP (Pa) of pressure loss after PM accumulation.

[0101] 〔Rate of increase (%) of pressure loss after PM accumulation due to PM accumulation〕

[0102] The increase ratio of the pressure loss after PM accumulation with respect to the initial pressure loss value P0 (Pa) (i.e., ΔP / P0 × 100%) was set as the rate of increase (%) of pressure loss after PM accumulation due to PM accumulation. The case where the rate of increase of pressure loss (%) was 350% or less was regarded as qualified.

[0103] (Examples 2 to 8 and Comparative Examples 1 to 13)

[0104] In Examples 2 to 8 and Comparative Examples 1 to 13, the respective raw materials used in the cordierite raw material were changed as follows to prepare the green clay. The average particle diameter, compounding ratio, and added water amount of the water-absorbing polymer, etc. in the raw materials were changed. Except for preparing the green clay using such raw materials, the green clay was prepared by the same method as in Example 1, and a honeycomb structure body having a partition wall structure as shown in Tables 1 to 3 was prepared.

[0105] Regarding the honeycomb structures of Examples 2 to 8 and Comparative Examples 1 to 13, the porosity and average pore diameter of the partition walls were also measured by the same method as in Example 1. The respective results are shown in Tables 1 to 3. In addition, regarding the honeycomb structures of Examples 2 to 8 and Comparative Examples 1 to 13, by the same method as in Example 1, the "initial pressure loss value P0 (Pa)", the "pressure loss value P1 (Pa) after PM deposition", the "pressure loss increase amount ΔP (Pa)" and the "pressure loss increase rate (%)" after PM deposition caused by PM deposition were obtained. The results are shown in Tables 1 to 3.

[0106] [Table 2]

[0107]

[0108] [Table 3]

[0109]

[0110] (Example 9)

[0111] As a forming raw material for preparing the green clay, a powder mixture of silicon carbide (SiC) powder and metallic silicon (Si) powder was prepared. Then, 9 parts by mass of a water-absorbing polymer, 1.0 part by mass of a binder, 2.0 parts by mass of an auxiliary agent, and 35 parts by mass of water were added as pore-forming materials to 100 parts by mass of the forming raw material to prepare the green clay. The water-absorbing polymer used as the pore-forming material was a water-absorbing polymer having a particle size of 10 μm. The starch used as the pore-forming material had a particle size of 6 μm. Hydroxypropyl methylcellulose and montmorillonite were used as the binder. Strontium carbonate and aluminum hydroxide were used as the auxiliary agent.

[0112] Next, using the obtained green clay, a honeycomb structure of Example 9 having a partition wall structure as shown in Table 4 was prepared by the same method as in Example 1.

[0113] (Examples 10 to 22 and Comparative Examples 14 to 29)

[0114] In Examples 10 to 22 and Comparative Examples 14 to 29, the raw materials for preparing the green clay were changed as follows to prepare the green clay. The average particle size, compounding ratio, and added water amount of the pore-forming materials and the like in the raw materials were changed. Except for preparing the green clay using such raw materials, the green clay was prepared by the same method as in Example 11 to prepare a honeycomb structure having a partition wall structure as shown in Tables 4 to 7.

[0115] Regarding the honeycomb structures of Examples 9 to 22 and Comparative Examples 14 to 29, the porosity and average pore diameter of the partition walls were also measured by the same method as in Example 1. The results are shown in Tables 4 to 7. In addition, regarding the honeycomb structures of Examples 9 to 22 and Comparative Examples 14 to 29, the "initial pressure loss value P0 (Pa)", the "pressure loss value P1 (Pa) after PM deposition", the "pressure loss increase amount ΔP (Pa)" and the "pressure loss increase rate (%)" caused by PM deposition were obtained by the same method as in Example 1. The results are shown in Tables 4 to 7.

[0116] [Table 4]

[0117]

[0118] [Table 5]

[0119]

[0120] [Table 6]

[0121]

[0122] [Table 7]

[0123]

[0124] (Results)

[0125] As shown in Table 1, it was found that the honeycomb structures of Examples 1 to 3 were able to suppress the increase in pressure loss during PM deposition compared to the honeycomb structures of Comparative Examples 1 to 5. In addition, in Table 1, honeycomb structures with the partition wall thickness T (μm) within a constant range were used as comparison objects.

[0126] Similarly, in each of Tables 2 to 7, it was also found that the honeycomb structures of the examples in each table were able to suppress the increase in pressure loss during PM deposition compared to the honeycomb structures of the comparative examples in that table. In Tables 2 to 7, honeycomb structures with at least one of the partition wall thickness T (μm) and porosity (%) within a constant range were used as comparison objects. In addition, it was found that among the honeycomb structures of each example, especially the honeycomb structures with the value of X being 150 to 300 were able to suppress the deviation of the pressure loss increase rate (%) caused by PM deposition to a small extent.

[0127] Industrial Applicability

[0128] The honeycomb structure of the present utility model can be used as a trapping filter for removing particulates and the like contained in exhaust gas.

[0129] Symbol Explanation

[0130] 1 - partition wall; 2 - compartment; 2a - inflow compartment; 2b - outflow compartment; 3 - outer peripheral wall; 4 - honeycomb structure portion; 5 - plugging portion; 11 - first end face; 12 - second end face; 16 - pore; 100 - honeycomb structural body.

Claims

1. A honeycomb structure, characterized in that: it has a columnar honeycomb structure portion, and the columnar honeycomb structure portion has partition walls arranged in a manner of surrounding a plurality of compartments that serve as fluid flow paths and extend from a first end face to a second end face; the partition walls are made of a porous body, and the porous body is formed with a plurality of fine pores that communicate the adjacent compartments sandwiching the partition walls with each other; a ratio L / T of a flow path length L of the fine pores in a thickness direction of the partition wall to a thickness T of the partition wall is defined as a tortuosity A, where the units of the flow path length L and the thickness T are μm; The average value of the curvature A of the partition walls constituting the honeycomb structure portion, that is, the average curvature A Ave is 1.10 to 1.40, and The average degree of curvature A Ave The value X obtained by dividing the deviation of the degree of curvature A by the square of the deviation degree of curvature B, i.e., the deviation degree of curvature B, is 100 to 300, where X = A Ave / B 2 .

2. The honeycomb structure according to claim 1, characterized in that: it further has a plugging portion, and the plugging portion is disposed at an opening portion on the first end face side or the second end face side of each of the compartments.

3. The honeycomb structure according to claim 1 or 2, characterized in that: a thickness T1 of the partition wall is 100 to 300 μm.

4. The honeycomb structure according to claim 1 or 2, characterized in that: a porosity of the partition wall is 35 to 70%.

5. The honeycomb structure according to claim 1 or 2, characterized in that: an average pore diameter of the partition wall is 8 to 30 μm.

6. The honeycomb structure according to claim 1 or 2, characterized in that: the X is 150 to 300.

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